DESALINATION

M odified and unmodified membrane samples w ere taken from different pilot-scale membrane plants after a sufficient operation period. One of t he plants is installed at a municipal drinking water t reatment plant, the second, a MBR, is located at a municipal wastewater treatment plant. The membrane samples have been cleaned using several c leaning solutions and the eluates were then analysed with LC-OCD. It was proven that Liquid ChromatographyOrganic Carbon Detection is a suitable and precise m ethod for the characterisation of foulants in regard to their molecular weights. Furthermore, it enables the analysis of the cleaning potential of several chemical solutions. While water has the l owest cleaning potential, in this study NaOH is t he most promising cleaning solution. Its effect o n foulants depends on residence time and d ominates even in basic aqueous solutions with o xidative chemicals such as NaOC1 and H20 z. N evertheless, oxidative chemicals have a good cleaning potential regarding removal of inorganic 1 1 1-~..O2-Plasma HzSO4pH 3 40°C 21 h 09 ~ ~Corona H2SO pH 3 40"C 21 h ~ :0 ~ ~ :6 unmodified HzSO' PH i°~iGillulhar Organ]cA ~d c s ' ~ -- 0 5 B uilding Blocks Humics A Low MolecularNeutrals D ~02 Retention TimeI min Fig. 9. LC-OCD chromatograms of H2SO4-solutions after cleaning of modified and unmodified membranes.